To prevent so-called relay station attacks (extension of the radio path from the vehicle to the vehicle key), it is a known practice to determine the distance between the vehicle key and the vehicle. The following problems now arise during this distance determination:
If the distance is determined using unencrypted radio signals, the distance measurement may be corrupted by a potential attacker. As a result, the previously mentioned relay station attacks become possible again by virtue of an attacker falsifying the distance measurement to be able to subsequently authenticate the vehicle key using the relay station attack.
If the distance is determined using encrypted radio signals, the distance cannot be determined accurately enough. This is due to the fact that the encryption of the signal sent back influences the response time (that is to say the period of time between the transmission of a radio signal to the radio key and the reception of the encrypted radio signal sent back from the radio key), on account of the period of time needed for the encryption, in such a manner that the distance can be determined only inaccurately on the basis of the response time.
Illustrative embodiments provide a method for authenticating a radio key for a vehicle and a vehicle.